Frequency synthesizer
AssigneeKing Fahd University of Petroleum and Minerals
InventorSaad Mohammad Al-Shahrani
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Abstract
The frequency synthesizer has two fixed frequency dividers, two charge pumps, five capacitors, a voltage controlled oscillator, and a transconductance voltage amplifier. The pulse widths of the input reference signal and the output signal are compared and the resultant signal is coupled to the oscillator to adjust its frequency. The circuit exhibits accurate frequency synthesizing, and thus can be used in wireless communication and signal processing systems. It provides a precise integer and fractional frequency division with a low phase noise. Moreover, it has a simple and compact structure that can be implemented in integrated circuit technologies such as CMOS.
Claims8
A frequency synthesizer, comprising:
- a reference fixed frequency divide-by-d divider having an input accepting a reference frequency signal, fref, outputs of the first fixed frequency divider being signals (1/d)fref and (1/d)fref, respectively;
- an output fixed frequency divide-by-d divider having an input that accepts an initial frequency signal, fo, outputs of the output fixed frequency divider being signals (1/d)fref and (1/d)fo, respectively;
- a first controlled switch bank having an input and a capacitively coupled output;
- a second controlled switch bank having an input and a capacitively coupled output;
- a transconductance amplifier having a first polarized input, a second, oppositely polarized input, and a capacitively coupled transconductance amplifier output;
- a first charge pump having inputs accepting the reference frequency signal, fref, and its complement fref, respectively, output of the charge pump being connected to the input of the first controlled switch bank, individual switches of the controlled switch bank being controlled by the outputs of the reference fixed frequency divider, the output of the first controlled switch bank being connected to the first polarized input of the transconductance amplifier;
- a second charge pump having inputs accepting the initial frequency signal, fo, and its complement fo, respectively, output of the second charge pump being connected to the input of the second controlled switch bank, individual switches of the second controlled switch bank being controlled by the outputs of the output fixed frequency divider, the output of the second controlled switch bank being connected to the second polarized input of the transconductance amplifier;
- a voltage controlled oscillator having a frequency control input connected to the transconductance amplifier output, and a pair of outputs, the outputs being the initial frequency fo, and its complement fo, respectively, the output pair being fed back to input of the second charge pump.
Dependencies are inferred from the claim text.